Apparatus for electrically marking metals



Nov. 16, 1937.

G. E. PRINTZ 2,099,622

APPARATUS FOR ELECTRICALLY MARKING METALS Filed March 21,

1935 2 Sheets-Sheet l INVENTOR ATTORNEY Nov. 16, 1937. G. E. PRlNTZ Y 2,099,622

APPARATUS FOR ELECTRICALLY MARKING METALS Filed March 21, 1935 2 Sheets-Sheet 2 1 /6 V w mtg GLf/V V f. PAW/V72 BY M A; wavy-QA- ATTORNEY Patented Nov. 16, 1937 UNITED STATES PATENT orrles means i mana'rus Ion Emc'rmcmr mama METALS Glenn it. Prints, Detroit, Mich.

Application March :1, 1m, Serial No. 1.2.101

3 Claims. (01. 175-301) This invention relates to apparatus for electrically marking metals, and to means for magneticalLv holding work during a marking or other operation, and for subsequently demagnetizing the work.

An object of the invention is to provide a very light and compact apparatus of the above mentioned character that may be conveniently carried to non-portable work, and which is adapted by the design and arrangement of its pole pieces to powerfully hold magnetizable work of almost any structural shape or form.

Another object is to provide in an improved and simplified manner for tapping the secondary coil of a transformer at predetermined points.

A further object is to so arrange said taps as to obtain a maximum number of voltage adjustments with a minimum number of taps.

A further object is to provide an improved tool for electrically. marking or engraving metal, which tool will produce either a fine or heavy mark, the electrode of which will last indefinitely, and will require no periodic refinishing, and which will be safeguarded against overheating of the electrode or undue heating of the operators hand.

These and various other. objects the invention attains by the construction hereinafter described,

and illustrated in the accompanying drawings, wherein; v

Fig. 1 is a perspective view of the apparatus, showing a piece of work engaged by the marking tool,

Fig. 2 is an end elevational view of the apparatus, partially in section,

Fig. 3 is a diagram. of the electricalconnections,

Fig.

Fi tool,

Fig. 7 is a sectional detail showing how an extra point for the marking tool is carried by the apparatus. 1

In these views, the reference characters I and 2 designate the primary and secondary coils of a portable transformer, adapted to also function as a magnetic work holder. Said coils are wound on a core '3 and between a pair of pole pieces 4, the core and pole pieces jointly forming a laminated U-shaped magnet.

Each pole piece is clamp d tightly by bolts between a pair of cast frame members 8, whereby the laminations are held firmly together so as 4 is a side elevational view, 5 is a top plan view, 6 is an axial sectional view of the marhng to prevent their relative vibration and resultant.

, the conductor l4 securely to said rod.

it considerable range.

humming. 1 The two frame members at each side of the U magnet areintegrally connected by a cross bar 1, and the two cross bars 1 engage opposite sides of the core 3, and pass through the coils. The frame members have leg portions ex- 5 tending below the coils to elevate thelatter above a supporting surface, and the upper ends of the pole pieces and framemembers jointly. form two coplanar, horizontal, work-supporing faces I and two inclined work-supporting faces a. The 10 faces -8 adjoin the relatively remote end faces of the pole pieces, while the faces I adjoin the coil-engaging faces of the pole pieces and converge downwardly toward the coils at approximately forty-five degrees to the coil axis.

The secondary coil is formed preferably of a single layer of fairly heavy wire and surrounds the numerous coils of relatively fine wire which form the primary coil. The terminals of'the primary coil are connected through a two-wire go cord II to an ordinary plug ll, adapting such. coil to be energized from the The secondary coil may be terminally connectedv through a conductor I! to a work-grounding plate I! and through a conductor I4 to a suitable as marking tool, best shown in 15g. 8."

This tool comprises a hollow handle I, formed preferably of wood having axially therein a heavy copper rod l8, having-a end portion projecting from the handle and terminally carrying an electrode 'II having the nature of a threaded rodgconsid'erably smaller in diameter than the rod II, and tapped into the latter and held fixed thereon by'alock-nut ll. Said electrode is formed of a metal such as steel. 36 capable of withstanding quite high temperatures and having a conductivity and cross-sectional area adequate to transmit the maximum required current without appreciable heating eflect, and has a pointed free end to the point of which is 40 welded (or otherwise moleoularly united) a tip Ila, formed of an alloy of tungsten or some other metal capable of indefinitely withstanding the exceedingly high temperatures to be induced at such tip. Interior-1y of the handle II, the rod Ii terminally carries a screw ll serving to fasten The current requirements for proper functioning of the marking tool vary considerably accordingly as light or heavy marking is desired and further must be suited to the electrical resistance of the work. It is therefore desirable to provide for such regulation of the secondary current, as will allow variationof its volume through Thus the secondary coil 66 is provided with a suitable number of taps 20, 21 22, 23, 24, and 25 so arranged as to ailord a wide range of variation in the eifective length of said coll. Thus said taps are arranged so that the lengths of secondary wire between taps 20 and 2| u- Connect to taps current 23 and 24- value tap connections a 21 and 22 20 21 and 20 3a 22 and 20 4a 22 and 23 5a 21 and 23 6a 25 and 23 7a 20 and 23 8a 22 and 24 9a 21 and 24 10a 22 and 25 11a 21 and 25 13a 20 and 25 Thus it is seen that the provision of the six taps shown not only permits a large selection of current values but also'permits, in many cases, a change from one current value to another by moving only one of the current take-ofi wires to a different tap. Preferably said taps are formed in a very simple manner as returnbent, outwardly projecting portions of the coil, looped at their bends to accommodate bolts 26 by which lead wires may be attached. Fig. 4, two of the taps are shown engaged by a pair of lead wires 27 leading one to the marking tool and the other to the grounding plate.

To facilitate carrying the described apparatus,-

there may be provided a handle comprising a pair of links 28 coaxially pivoted to the pole pieces 4 and carrying and connected by a hand piece 29 formed of suitable non-magnetic materlal.

An extra electrode am. is normally screwed into a socket 30 of one of the frame members,

and with its lock-nut I8a,may serve as a binding post, if desired, for grounding the conductor l2 to the frame, rather than to the plate 13 when desired.

In use of the described apparatus, a piece of work 3! may be positioned, inwhole or in part, on the grounding plate, so that the secondary circuit will be closed through the work to the electrode it when the latter is applied to the work. Because of the high resistance prevailing at the point of contact of the electrode and work, there is generated at such point a high heat, acting to discolor the work and to form a depression therein if the position of the electrode is maintained. By moving the electrode over the work at a suitable speed, the work may be marked to any desired depth with any desired design, words or numerals. Generally the tool may produce a suitable mark by moving it at a gradual speed, as in writing with a pencil.

It will in some cases be found convenient to dispose work for marking in a bridging relation to the pole pieces 4, where it will be magnetically held in place. When the size and shape of the work permits, it will be engaged with the convergent pole faces 9, since there prevails 2.

,proper engagement with work with a minimum provision insures that all joints are readily actends to deter chance users of the machine from stronger field between these faces than that between the coplanar faces, and since the convergent faces exercise a wedging effect tending to more firmly hold the work.

A switch 21 controlling the primary coil is preferably conveniently mounted on one of the pole pieces 4.

Employment of only one pair of poles, as disclosed, is highly desirable, since the resulting magnetic field across the gap is of maximum concentration for a given current, and a concentrated flux is essential to quick and complete magnetization and demagnetization of the work, particularly when of high magnetic retntivity.

Complete and ready portability is achieved in the described construction by elimination of inactive parts and elements and by extreme compactness' and low weight. Ready portability is highly desirable, as the work in many cases will be not readily portable.

Provision of the two differential pairs of pole faces 8 and 9 adapts the apparatus to work widely varying in shape and size, and the larger clearance space about the pole faces permits their of interference due to projections on the work. The apparatus is especially well suited to magnetization and demagnetization of small parts of extreme hardness, because of the high density and constancy of the magnetic field, and the ample space between the poles for accommodation of such parts.

In using the apparatusto magnetize or demagnetize a large number of quite small parts, the same may be retained in suitable bags or the like, in being disposed between the poles.

The V-form of the faces 9 particularly adapts said faces to engage long bars of work, since it eliminates the tendency to slip or roll off that prevails when the work engages fiat faces. The V-shepe further adapts round or cylindrical objects to be completely and uniformly magnetized throughout by rotating the same between the convergent walls. 1

The apparatus, by reason of the high density and volume of its field, may be employed in freeing and making workable various compounds and liquids in metal cases or containers by a mere application of the poles to such containers, so as to induce through the latter a heavy short circuited flow of current such as will gently heat the container while avoiding the dangerous use of flames for that purpose. Similarly, the apparatus may be employed to moderately heat parts to effect their expansion or for any other reason.

Formation of the taps as integral portions of the secondary coil eliminates joints between the taps and coil, and relatively complex switching devices heretofore employed with attendant expense, loss of current, and upkeep. Also, this cessible for inspection, and guards against either gradual or sudden falling off of conductivity in the secondary circuit.

Furthermore, the use of bolted tap connections experimentally changing from one tap to another, with detriment to the resulting work.

In prior apparatus for electrically marking metals, it has been necessary to quite frequently refinish or discard the electrodes owing to their deterioration by heat. In the described apparatus, the provision at the electrode point of a very highly heat-resistant alloy safeguards the electrode against deterioration over a long period of time. The threaded engagement of the electrode with the copper rod I6 is such as to establish a fully adequate thermal and electrical connection between said parts. The thermal connection at this point is vital in assuring conduction to the copper rod l6 of any excess heat generated in the electrode, the copper rod being of adequate size to readily dissipate such heat by radiation. The bend in the exterior portion of the rod l6 serves to dispose the electrode at a convenient angle to the handle of the tool-for conveniently marking work.

The invention is presented as including all such modifications and changes as come within the scope of the following claims.

What I claim is:

1. A work-holding electro-magnet comprising a magnetizing coil, a magnetizable laminated core within the coil, having a pair of pole pieces at its ends, projecting similarly beyond the coil periphery and having coplanar work-seating faces and also having work-seating faces convergent toward the coil, and a pair of frame members clamping the laminations together, and projecting beyond the coil coextensively with the laminations and having upper end faces approximately flush with the said work-engaging faces.

2. A portable transformer comprising U- shaped laminations forming a core and pole pieces, primary and secondary coils wound on said core between the pole pieces, a pair of H- shaped frame members between which the laminations are clamped and comprising cross bars extending through said coils and at opposite sides of the core portions of said laminations, the lower portions of said frame members forming supporting legs for the transformer, and said frames jointly forming pockets beneath the pole pieces for electrical connections to the coils.

3. A work holding electro-magnet, comprising a magnetizing coil, a magnetizable core within the coil, having a pair of pole pieces projecting similarly beyond the coil periphery and having coplanar work-seating faces and also having work-seating faces convergent toward the coil, the core and pole pieces being laminated, a pair of frame elements clamping the laminations'together and formed with bars extending through the coil, one at each side of the core, and clamping connections between the frame members.

GLENN E. PRINTZ. 

